Half-Life: Alyx performance analysis (or: why low graphic settings produce a sharper image)

Steam VR render scale

Steam VR settings

Alyx dynamic resolution

Resolutions per fidelity level. Steam resolution is 2188 x 2432.
The algorithm chooses a higher fidelity level for less complex scenes , such as looking towards the sky
Gif cycling different fidelity levels. Notice how the GPU time graph increases with the level.

Graphics options

“low” settings on the left, “ultra” settings on the right
“High” settings with some tweaks
GPU time increase (in ms) per graphic setting
  • “shadows” to “medium” or “high”
  • “fog” to “medium”


MSAA level comparison (check out the tree branches)
GPU time for different MSAA values and fidelity levels
fidelity level VS MSAA level

Motion smoothing

Laptop optimization (aka: why nvidia Optimus sucks)

integrated GPU utilization when VR View is enabled in the laptop’s screen
CPU and GPU utilization increase when VR View gets enabled in laptop’s screen

VR View & Spectator view cost in desktop systems

GPU time when steam’s VR View is shown or hidden


  • Disable Steam VR’s “motion smoothing”
  • Set the headset’s refresh rate to 80Hz or 90Hz instead of 120Hz. The lower the refresh rate, the longer the GPU time window and thus the higher the fidelity level (resolution) the game will choose.
  • Set Steam VR’s render resolution to 100%. Higher values are not needed for Alyx.
  • Change the graphic options as follows: “characters” to “low”, “fog” to “low” or “medium”, “shadow” to “medium” or “high”
  • Minimize the spectator window if you’re using a laptop and close Steam’s VR View window (if open).




Android & former iOS developer https://horizon.camera/

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Petros Douvantzis

Petros Douvantzis

Android & former iOS developer https://horizon.camera/

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